Heat input adjustment process for unsupported aluminum alloy lattice struts continuous forming by wire arc-directed energy deposition

Metal lattice structures with lightweight and multifunctionality characteristics have attracted increasing attention in recent years owing to their good mechanical properties, which can further be improved by applying nanoparticle-modified aluminum alloys to lattice structures. However, current manufacturing technologies limit the development of large-size and complex aluminum alloy lattice structures. Herein, a novel unsupported additive manufacturing method based on wire arc-directed energy deposition (WA-DED) was explored for the fabrication of lattice structures. This method realized the continuous forming of unsupported lattice struts by controlling the arc heat input based on the established theoretical models. The models consisted of a heat transfer model taking into account both heat conduction and heat convection for molten pool temperature stabilization, as well as a force model to ensure molten pool force stabilization. Process windows of heat input of unsupported struts were then developed based on the theoretical models followed by validation by numerical simulation. Unsupported nanoparticle-modified aluminum alloy lattice struts with different diameters and angles were fabricated using WA-DED technology, which exhibited refined microstructures with grain sizes smaller than 20 mu m and excellent mechanical properties with ultimate strengths and breaking elongation exceeding 400 MPa and 7 %, respectively. Finally, high-quality pyramid lattice structures were efficiently fabricated using the unsupported additive manufacturing method. Overall, the proposed method fills the gap in the efficient preparation of large-size aluminum alloy lattice structures. The developed model can also broadly be extended to the unsupported additive manufacturing of other materials, such as titanium, steel, and magnesium alloys.